A variety of microwave devices such as frequency modulated oscillators, amplifiers, filters, resonators, wavemeters, etc. include a waveguide or other microwave cavity supporting electromagnetic waves. The electromagnetic waves resonate in the cavity at a resonant frequency. The cavity may be tuned with a metallic screw, probe, or other sliding short circuit type of plunger that extends through a wall thereof to change the resonant frequency.
A problem with a conventional tuning element is that at least some portion of the tuning element and/or the driving unit for driving the tuning element extends out of the cavity for operator access. For example, a sliding plunger inside a cavity is connected to a drive unit outside of the cavity. As another example, a tuning screw extending inside a cavity includes a portion extending out of the cavity. Accordingly, the total volume of the cavity and the tuning element is unnecessarily large. Further, the portions extending out of the cavity may be exposed to accidental contact which can change the tune of the cavity.
Furthermore, conventional tuning elements lack the ability to be removed and replaced with another tuning element having a different configuration for controlling the electrical response of a cavity. For instance, by using tuning elements with different configurations, the passband characteristics of a cavity can be quickly changed. Further, by using tuning elements with different configurations and then securing these tuning elements to a common position relative to a cavity, the passband characteristics of the cavity can be changed even quicker.
Previously, more piece parts and structure were needed to be used for a given cavity. Consequently, at times, entire units have to be scrapped because of limited frequency flexibility due to physical inflexibility.